Such needle assemblies, also known as blood collection needles are known in the art. The needle assembly is used e.g. by the medical practitioner in daily hospital routines. The first needle portion is placed within a patient's vein. Before or thereafter, a container having a rubber port is coupled with the second needle portion by sticking the second needle portion through the rubber port such that it protrudes into the hollow interior space of the container. In the following, the patient's blood can pour into the container. When the container is sufficiently filled with blood, it can be retracted from the second needle portion by the medical practitioner. Thereby, the rubber port sealingly closes again and the procedure can be repeated for receiving a further blood sample.
A critical step in the above described procedure is when the medical practitioner tries to place the first needle portion within the patient's vein. In particular in case of patients having a low blood pressure, as children, it can be difficult to locate the patient's vein. In those instances, it is advantageous to have a feedback indicating the medical practitioner if vein entry has been achieved. Such a feedback is usually called a flashback. When the vein entry is achieved, a particular portion of the needle assembly is filled by the patient's blood and thereby indicates to the medical practitioner the successful vein entry.
The European patent application EP 2 670 306 A1 shows a blood collection needle having a flashback feature. However, this prior art device has a complicated structure and is difficult and expensive to manufacture.
The European patent application EP 1 796 539 A1 shows another blood collection needle with a flashback feature. However, this device does not provide quick flashback indication, as is air included within the flashback chamber cannot pour out quickly enough.
The European patent application EP 2 097 123 A1 shows a further blood collection needle with a flashback feature. A punctured needle extends through a housing surrounding the needle in the punctured section. The housing provides a flashback chamber. A filter is arranged in one of the housings outer walls. However, this device has the drawback that the flashback chamber is formed by a large lumen such that undesired large amount of patient's blood is collected for flashback purposes. The same drawback applies for the prior art documents according to the European patent applications EP 2 042 089 A1 and EP 2 490 592 A1.